1. Field of Invention
The present invention relates to a hoist such as an electric chain hoist and, more specifically, to a hoist equipped with a power-off type electromagnetic brake allowing manual lowering of a load at the time of a power failure or the like.
2. Description of Related Art
Conventionally, as an electric chain hoist allowing manual lowering at the time of a power failure, there has been well-known an electric chain hoist which is provided with a brake releasing wedge member to be driven into a gap portion between a brake base of an electromagnetic brake portion and an armature and which has, in a surrounding wall portion of a brake casing to which the electromagnetic brake portion is mounted, a driving-in hole into which the wedge member is to be inserted, wherein, at the time of a power failure or the like, the brake releasing wedge member is driven into the gap portion between the brake base and the armature to release the electromagnetic brake, thus allowing manual lowering (JP-1-85397 A (Utility Model)).
3. Technical Problems
In the above-mentioned prior-art technique, the brake releasing wedge member is inserted into a driving-in radial hole provided in the wall portion of the brake casing, and the wedge member is driven into the gap portion between the brake base and the armature by a striking tool such as a hammer to enlarge the gap portion between the brake base and the armature, thereby releasing the electromagnetic brake portion and placing the brake disk and the armature in a non-contact state; and, in this state, load lowering is manually performed by a handle mounted to an end portion of a motor rotation shaft; after the wedge member has been driven into the gap portion between the brake base and the armature, the brake remains released, so that it is impossible to adjust the brake force at the time of lowering the load; thus, it is impossible to adjust the load lowering speed; further, the wedge member is inserted into the driving-in hole provided in the brake casing, and is driven into the gap between the brake base and the armature by a striking tool such as a hammer, so that, when the wedge member becomes loose, the brake is engaged, making it difficult to smoothly perform the operation of lowering the load; further, the wedge member will be detached from the driving-in hole to be dropped.